Not my kind of renewable

It was a few months ago now when a friend of mine asked me what I was doing that Friday night (and as usual I had nothing planned). They were messaging to see if I wanted to go to a fundraiser dinner and movie that night. After very little hesitation, and organizing what wine we wanted to buy, we set off to the club rooms for the event. For some context, the club that was hosting this fundraiser was the Melbourne University Mountaineering Club, the event was raising funds towards buying legal aid for a group trying to protect a river in Peru (and the wine was a pinot noir). Leading up to the event I had not paid much attention to what the movie was about as I was a new member of the club and wasn’t good friends with anyone involved in running it.

Upon getting there, and finding myself a plate of food, I sat down to what was a very interesting and thought-provoking evening.

The movie, Dam Nation, was a documentary about the history of dams and hydroelectric power plants in the USA. My main thought on dams and hydropower up to that point (mainly influenced by school) was “it’s a renewable energy source, I’m sure it’s fine”. This movie drastically changed that. When a dam is constructed, it affects the river in three main ways; it reduces fish habitat, it alters river flow and it blocks stilt flow.

Image: commons.wikimedia.org

How does damming a river cause these changes and why is that an issue?

Reducing fish habitat

A large proportion of the fish on the plant spend at least some part of their lives in a river, whether they be freshwater fish who spend their whole life in rivers and lakes, or fish like salmon who lay their eggs, far upstream in rivers. This becomes a problem when there is a huge wall of concrete in their path, stopping them from reaching upstream spawning grounds or other food sources. Often the presented solution to this is having a fish ladder, which works in principle, but they are often a costly measure that scales with the height of the dam. (see http://e360.yale.edu/features/blocked_migration_fish_ladders_on_us_dams_are_not_effective for more information)

Alters river flow

Normally river levels will go up and down, depending on when it last rained or when the snow started to melt in the nearby mountains. This results in the semi-regular flooding of riverbanks or the river flowing into small tributaries. This is a vital part of the river ecosystem as it creates small micro-ecosystems, which may be vital for the survival of some species of plants and animals. When a river is dammed, the water is often let out at a constant rate, resulting in flooding events happening less frequently and often to a lesser extent. This means that the species that require these events to happen can no longer survive.

Blocks silt flow

When a river flows, not just water flows downstream. A huge amount of dirt and silt is washed down, too. This is hugely important for the ecosystems downstream where nutrients in the silt are used to feed the plants and animals. If a river is dammed, the water slows down when it gets to the dam, causing the sediment to settle on the riverbed and not move past the dam. This has the effect of starving the plants and animals in the river downstream of some of the nutrients necessary for life.

Damming a river can also have detrimental effects on the communities living around it. Often whole villages or towns will have to move due to dam construction leading to the flooding of their home. The rising waters behind the dam can also decimate priceless archaeological or irreplaceable religious sites, causing permanent harm to communities.

Parts of me were shocked and saddened about the detrimental effects that dams are having on our ecosystem, while part of me was angered. Why was I not told about this before? And why are kids taught that hydropower is a “clean” or “renewable” energy source when it clearly has harmful effects on the ecosystems of the rivers that they touch? The movie ended on a happier note, however, showing the removal of a dam in the US as well as highlighting the growing awareness around the issue. To me, this movie outlined that it pays to look into what you were taught in school as some ‘facts’ are often not the whole truth.

For more information on Dam nation or the Maranon waterkeeper project see the links below.

2 Responses to “Not my kind of renewable”

My main “message” is that dams aren’t all nice and that they shouldn’t be labeled as so. Yes, the location of the dam will affect its environmental impact, but I imagine that the overwhelming majority of large dams have negative effects on the local ecosystem. I would also imagine that the cost of retrofitting a dam to generate power and be less damaging to the local ecosystem would be a very costly measure and that sourcing power from wind or solar would be less environmentally impactful.

Dams can have significant impacts on ecosystem function. Several large dams proposed on the Salween River in Myanmar threaten unique limestone features and ecosystems. No where on earth are they as extensively and intricately developed as around the confluence of the Salween and upstream into the Pang River. A proposed dam near this confluence will destroy these features.

But what is your view on the retrofitting of existing dams and utilising the power that they might generate? Are you saying that hydro power is a negative per se or that its about the location, characteristics and impact of each individual dam?